Field of the Invention
The present invention relates to a method for producing a liquid-ejection-head substrate and to a liquid-ejection-head substrate produced by the method.
Description of the Related Art
Liquid ejecting devices, such as ink jet printing devices, include a liquid-ejection head. The liquid ejection head is provided with a liquid-ejection-head substrate, called a chip or the like. The liquid-ejection-head substrate includes an energy-generating element, such as a heating resistor or a piezoelectric element. The energy-generating element energizes liquid to cause ejection of the liquid. In such a liquid-ejection-head substrate, a flow channel and a liquid chamber are formed on a substrate formed of silicon or the like and an energy-generating element is disposed in the liquid chamber. On the substrate, the energy-generating element is connected to a wiring layer and an end of the wiring layer functions as a pad. The pad is connected to a power supply provided outside the liquid-ejection-head substrate via external wiring, such as by bonding. The energy-generating element in the liquid-ejection-head substrate is driven by supplying electricity from the outside of the liquid-ejection-head substrate via the pad.
The pad includes a wiring layer formed of aluminum or the like and a bump section formed of gold or the like. A process for producing a liquid-ejection-head substrate may involve electrically inspecting a semiconductor integrated circuit in the wiring layer in the pad by using a contact probe. In this electrical inspection, the contact probe is brought into contact with the surface of the wiring layer in such a manner that the wiring layer is scrubbed with the contact probe. At this time, an insulating film, such as a naturally oxidized film, and the wiring layer formed of aluminum or the like are scrubbed with the contact probe, forming a protruding electrical inspection mark on the wiring layer in the pad. Even after subsequent washing, such a protruding electrical inspection mark remains on the pad. For example, when an organic material is stacked on the substrate, such an electrical inspection mark may reduce the thickness uniformity of a layer of the organic material. If the electrical inspection mark cannot be appropriately covered by a barrier metal layer formed after the electrical inspection, alloying may occur between the wiring layer (formed of, for example, aluminum) and a bump section (formed of, for example, gold) which are stacked with the barrier metal layer therebetween, and this alloying may decrease the function as an electrode.
Japanese Patent Laid-Open No. 2010-221656 describes that a plurality of stepped portions (slits) is formed in a region with which a contact probe is to be brought into contact and the plurality of stepped portions (slits) serves as a stopper layer and reduces formation of an electrical inspection mark on a wiring layer in a pad.
The method described in Japanese Patent Laid-Open No. 2010-221656 may reduce formation of an electrical inspection mark. However, according to the inventors' studies, the stopper layer may be damaged when the contact strength of a contact probe is high during electrical inspection, or when the stylus pressure applied to a first contact probe is high due to uneven lengths of contact probes. As a result, a protrusion (electrical inspection mark) may be formed on the wiring layer.
The size of the electrical inspection mark depends on the conditions of an inspection device. However, when the contact strength of a contact probe for scrubbing an insulating film is adjusted to reduce formation of the electrical inspection mark, the insulating film may be left, which may result in uneven resistance.